The burning rates of solid propellant compositions have been increased by various innovations which have included metal oxides, metal staples, and organometallic compounds including carborane and ferrocene compounds. One of the most widely used materials for improving burning rates has been metal staples. Metal staples in the form of multidimensional crosses have been used. The staples have been of various cross sectional shapes including rectangular, square, or circular. Aluminum metal has been one of the most widely used metal since it has been readily available at an economical price. Aluminum and other metals have been introduced as particles in the form of continuous wires or ribbons, short wires or ribbons, chopped foil, platelets, flake, and the like.
The prior art has performed experimentation with composite staples consisting of layers of a propellant fuel metal (e.g., aluminum and a ferromagnetic metal, e.g., nickel). The prior art has taught that ferromagnetic metal detracts from propellant performance, but the detrimental effects are minimized when a minimum effective amount is employed in order to control staple orientation using an applied magnetic field. The detraction of the ferromagnetic metal from propellant performance is offset by a gain due to staple orientation which is most effective when the staple is oriented perpendicular to burning surface. The prior art metal composite for the described use employed epoxy resin or coating, one on the other, to bond the two metals together.
More recently graphite linters and aluminum whiskers have been employed in solid propellant compositions as mechanical burning rate accelerators. The function of the graphite linters and aluminum whiskers take place at the combustion site whereby heat generated at the combustion site is conducted into the propellant grain to further promote the propagation of the flame front and thereby accelerate the burning rate.
A modification in the structure of the graphite linters and aluminum whiskers which results in an increase of their function would be an advantage since a higher acceleration rate to the burning rate could be achieved with the same weight percentage employed. A further advantage is recognized in that graphite linters and aluminum whiskers having a higher efficiency would enable the same burning rate to be retained while employing a lesser weight percentage in the propellant composition.